Add TransactionalFileWriter

include/athena/FileWriter.hpp

@@ -66,6 +66,56 @@ private:
     atUint64     m_bytePosition;
     bool         m_globalErr;
 };
+
+class TransactionalFileWriter : public IStreamWriter
+{
+#if _WIN32
+    std::wstring m_filename;
+#else
+    std::string  m_filename;
+#endif
+    bool m_overwrite, m_globalErr;
+    std::vector<uint8_t> m_deferredBuffer;
+    atUint64 m_position = 0;
+public:
+    TransactionalFileWriter(const std::string& filename, bool overwrite = true, bool globalErr=true)
+    : m_overwrite(overwrite), m_globalErr(globalErr)
+    {
+#if _WIN32
+        m_filename = utility::utf8ToWide(m_filename);
+#else
+        m_filename = filename;
+#endif
+    }
+    TransactionalFileWriter(const std::wstring& filename, bool overwrite = true, bool globalErr=true)
+    : m_overwrite(overwrite), m_globalErr(globalErr)
+    {
+#if _WIN32
+        m_filename = filename;
+#else
+        m_filename = utility::wideToUtf8(filename);
+#endif
+    }
+
+    void flush()
+    {
+        if (m_deferredBuffer.size())
+        {
+            FileWriter w(m_filename, m_overwrite, m_globalErr);
+            w.writeUBytes(m_deferredBuffer.data(), m_deferredBuffer.size());
+            cancel();
+        }
+    }
+
+    void cancel() { m_deferredBuffer.clear(); m_position = 0; }
+
+    inline atUint64 position() const { return m_position; }
+    inline atUint64 length() const { return m_deferredBuffer.size(); }
+    void seek(atInt64 pos, SeekOrigin origin = SeekOrigin::Current);
+    void writeUBytes(const atUint8* data, atUint64 len);
+
+    ~TransactionalFileWriter() { flush(); }
+};
 }
 } // Athena
 

src/athena/FileWriter.cpp

@@ -16,7 +16,11 @@ FileWriter::FileWriter(const std::string& filename, bool overwrite, bool globalE
       m_bytePosition(0),
       m_globalErr(globalErr)
 {
+#if _WIN32
+    m_filename = utility::utf8ToWide(m_filename);
+#else
     m_filename = filename;
+#endif
     open(overwrite);
 }
 
@@ -25,7 +29,11 @@ FileWriter::FileWriter(const std::wstring& filename, bool overwrite, bool global
       m_bytePosition(0),
       m_globalErr(globalErr)
 {
+#if _WIN32
+    m_filename = filename;
+#else
     m_filename = utility::wideToUtf8(filename);
+#endif
     open(overwrite);
 }
 
@@ -121,5 +129,33 @@ void FileWriter::writeUBytes(const atUint8* data, atUint64 len)
     }
 }
 
+void TransactionalFileWriter::seek(atInt64 pos, SeekOrigin origin)
+{
+    switch (origin)
+    {
+    case SeekOrigin::Begin:
+        m_position = pos;
+        break;
+    case SeekOrigin::Current:
+        m_position += pos;
+        break;
+    case SeekOrigin::End:
+        break;
+    }
+}
+
+void TransactionalFileWriter::writeUBytes(const atUint8* data, atUint64 len)
+{
+    atUint64 neededSz = m_position + len;
+    if (neededSz > m_deferredBuffer.size())
+    {
+        m_deferredBuffer.reserve(neededSz * 2);
+        m_deferredBuffer.resize(neededSz);
+    }
+
+    memmove(m_deferredBuffer.data() + m_position, data, len);
+    m_position += len;
+}
+
 }
 } // Athena